3pPP11. Effects of interaural configuration of wideband forward and
backward fringes on detection of an interaural phase shift of a narrow portion
of wideband noise.

Threshold interaural phase shifts were measured for a 20-Hz-wide section
(CF=500 Hz) of wideband noise. Each interval of a 2-afc task consisted of an
observation interval (either 100 or 250 ms), and forward and backward temporal
fringes, all having identical amplitude spectra. A spectral band (250, 500, or
750 Hz wide) surrounding the target band was diotic throughout the entire
stimulus presentation. Interaural phases of frequencies above and below the
diotic band (flanking bands) differed for the temporal fringes and the
observation interval. For one set of conditions, the flanking bands were diotic
during the temporal fringes and interaurally phase-shifted (plus or
minus)90(degrees) during the observation interval. In other conditions, the
flanking bands contained the 90(degrees) interaural phase shift in the temporal
fringes, and were diotic in the observation interval. In general, thresholds
were higher for conditions in which the temporal fringes were completely
diotic, compared to conditions in which the interaural parameters of the
flanking bands initially differed from the diotic band surrounding the target.
This difference in thresholds decreased as the width of the diotic band and the
duration of the observation interval increased. [Work supported by NIH.]